A297309 Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 or 2 neighboring 1s.

4, 23, 117, 609, 3159, 16389, 85041, 441225, 2289339, 11878281, 61631001, 319774761, 1659164103, 8608637997, 44666257401, 231752633913, 1202457662523, 6238998904833, 32371291359585, 167959719216009, 871465613342823

Offset: 1

Author

R. H. Hardin, Dec 28 2017

Keywords

• nonn

Examples

			Some solutions for n=5:
..1..1..1. .0..1..0. .1..1..0. .0..1..0. .1..1..0. .0..0..0. .1..1..0
..0..1..0. .1..0..0. .1..1..1. .1..0..1. .1..1..0. .0..0..0. .1..1..1
..1..0..0. .1..1..1. .0..0..0. .0..1..0. .1..0..1. .0..0..0. .0..0..0
..0..0..1. .0..1..0. .1..1..1. .1..1..0. .0..1..0. .1..1..0. .0..1..0
..1..1..0. .0..1..1. .0..1..1. .0..0..0. .0..1..1. .1..1..1. .1..1..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Column 3 of A297314.

Formula

Empirical: a(n) = 3*a(n-1) + 11*a(n-2) + 3*a(n-3) - 6*a(n-4).

Empirical g.f.: x*(4 + 11*x + 4*x^2 - 7*x^3) / (1 - 3*x - 11*x^2 - 3*x^3 + 6*x^4). - Colin Barker, Feb 26 2019